This invention relates to wipes that have been impregnated with biliquid foam surface treating liquids, such as a furniture polish or cleaner. In particular, it relates to such wipes where the liquid is stable and resistant to migration through a wipe in response to gravity.
Wipes have been previously been impregnated with a wide variety of cleaning, polishing, and other treating liquids. See e.g. U.S. Pat. Nos. 4,725,489, 4,753,844, 4,963,432, 5,914,177, 6,121,165, 6,136,775 and 6,270,878. Pre-impregnated wipes are particularly advantageous because they simultaneously apply the desired liquid to the surface to be treated, spread the material along the surface, and remove undesired materials. In the case of a furniture polish wipe, the wipe can also act as a buffer.
For example, in U.S. Pat. No. 3,965,518 it was proposed to impregnate cellulosic wipes with a furniture polish containing, among other things, water, mineral oil, silicon oil, nonionic surfactant and/or anionic surfactant, preservative and pH adjustor, in an emulsion form. However, emulsions have a tendency to migrate with gravity when such wipes are stacked in a container for storage. Thus, wipes at the top of the stack tended to have less impregnating polish.
Moreover, some emulsions tend to interfere with the effectiveness of some antimicrobial agents. This can be a particular problem with respect to wipes designed to have an antibacterial effect on the surfaces that they treat.
Further, some emulsions are not stable long term absent use of high levels of surfactant. High levels of surfactant may cause residue problems, particularly in the field of furniture polishes.
Particularly desirable ingredients in furniture polishes are silicone oils. However, conventional emulsions tend to have stability problems when they contain silicone oils absent the use of a hydrocarbon solvent. Such hydrocarbon solvents can be undesirable due to environmental or flammability concerns.
In unrelated work the art has developed oil-in-water dispersions known as biliquid foams. In these dispersions the oil is present in discrete droplets surrounded by a first surfactant. The remaining water has dissolved in it a second surfactant. The second surfactant migrates to the surfactant-coated surface of the oil to create at least some drops (preferably most oil drops) surrounded by a bilayer of surfactant. See generally U.S. Pat. Nos. 4,486,333 and 6,312,760. See also F. Sebba, Biliquid Foams-A Preliminary Report, 40 J. Colloid. Interface Sci. 468-474 (1972); O. Sonneville-Aubrun et al., Surfactant Films In Biliquid Foams, 16 Langmuir 1566-1579 (2000) and a Disperse Technologies Limited 1998 technical presentation entitled “Advanced Topical Dispersion Technology”.
Early versions of these foams suffered from significant instability. However, U.S. Pat. No. 6,165,479 teaches that by adding a viscosity modifier/thickener to such foams can markedly increase the stability of the foam. However, this patent was largely focused on formulating cosmetics, and did not address design problems in creating formulations for wipes.
Thus, a need still exists for improved impregnated wipes, particularly those that resist the tendency of gravity to cause the impregnating liquid to migrate to the bottom of the stack.